Eight-year-old daria was having some disturbances in her sleep, so her parents took her to a children's hospital in her state to undergo various tests. though she was young, she recalls having to sleep in the hospital room with a bunch of wires stuck to her scalp. she also remembers the doctor telling her parents that the computerized print out of her brain waves offered clues as to why she was having such difficulty sleeping. what device was used in daria's sleep study?